Figure out which man sections to use... does anyone read them
Docs should mention flow and structure.
When deleting a newsgroup, safer to remove all references to that
newsgroup in the database, rather than scanning for IDs, and then
Use xover for filtering.
If the file .filter exists, then have snfetch run BINDIR/snfilter,
which sends XOVER and does some processing, passing the output to
.filter shell script. The output of this whole chain to snfetch is
a series of number id lines, which represent the desired articles.